Parasites were the inspiration behind the creature that terrified moviegoers in Alien. Now sci-fi screenwriters may have a new role model—parasitic worms that brainwash their victims. Scientists say hairworms, which live inside grasshoppers, pump the insects with a cocktail of chemicals that makes them commit suicide by leaping into water. The parasites then swim away from their drowning hosts to continue their life cycle. A team of French biologists made the discovery after monitoring grasshoppers that became trapped in a swimming pool in southern France. Postmortems of the grasshoppers suggest that worms triggered the insects' death leaps by sabotaging their...